Potassium is the fourth element in the first column of the periodic table. It is classified as an alkali metal. Potassium atoms have 19 electrons and 19 protons with one valence electron in the outer shell. Potassium is considered chemically similar to sodium, the alkali metal above it on the periodic table.

Characteristics and Properties

Under standard conditions potassium is a soft silvery-white metal. It is so soft that it can be easily cut with a knife. When cut, the exposed metal tarnishes quickly and forms a dull oxide coating.

Potassium has a very low melting point such that even a candle can cause it to melt. When it burns, it produces a pale purple colored flame. Potassium also has a very low density and is the second least dense metal after lithium. It is so light that it can float in water.

Chemically, potassium is a very active metal. It reacts violently when coming into contact with water, producing heat and hydrogen gas. It also reacts with many other elements and substances such as oxygen, acids, sulfur, fluorine, and nitrogen.

Where is potassium found on Earth?

Because potassium reacts so readily with water, it is not found in its elemental form in nature. Instead it is found in various minerals such as sylvite, carnallite, langbeinite, and kainite. Most minerals that contain potassium are referred to as potash.

Making up about 2.1% of the weight of the Earth's crust, potassium is the eighth most abundant element in the crust. It can also be found in ocean water where it is also about the eighth most abundant element.

How is potassium used today?

The largest use of potassium is potassium chloride (KCl) which is used to make fertilizers. This is because potassium is important for plant growth.

Potassium also plays a vital role in our bodies. It is used in muscle contraction, fluid and pH balance, bone health, and helps to prevent kidney stones. It is about the eighth most abundant element in the human body by weight.

How was it discovered?

Potassium was first isolated by English chemist Sir Humphry Davy in 1807. He used electricity to separate the element from the salt potash.

Where did potassium get its name?

Potassium gets its name from the salt potash from which potassium was first isolated. The K symbol for the element comes from the Latin word "kalium", which means potash.

Isotopes

There are three isotopes of potassium that occur naturally: K-39, 40, and 41. The majority (93%) of potassium found in nature is K-39.

Interesting Facts about Potassium

Potassium chloride (KCl) is sometimes used as a substitute for table salt.

The USDA recommends that adults consume 4.7 grams of potassium each day.

A small amount of potassium can taste sweet. A higher concentration can taste bitter or salty.

Potassium bicarbonate is the chemical name for baking soda. It is used in fire extinguishers, baking powders, and antacids.

Some good sources of potassium in our diet include bananas, avocados, nuts, chocolate, parsley, and potatoes.